The enforcement branch
Transaction mechanism to ensure data consistency.
Transaction should have four properties: atomicity, consistency, isolation, durability. These four properties are usually called ACID properties.
- Atomicity (atomicity). A transaction is an indivisible unit of work, all operations in the transaction include either do or do not do.
- Consistency (consistency). The database transaction must be changed from one consistent state to another consistent state. Consistency and atomicity are closely related.
- Isolation (isolation). Execution of a transaction can not be other transactions interference. I.e., operation and use of the data inside a transaction other concurrent transactions are isolated and can not interfere with each other between the respective transaction executed concurrently.
- Persistence (durability). Persistent, also known as permanent (permanence), means that once a transaction commits, changing the data in the database http://www.weixiu3721.com/ it should be permanent. The next operation or other faults should not have any effect on them.
Python DB API 2.0 provides two methods of transaction commit or rollback.
Example:
For transactional database, database programming in Python, when the establishment of the cursor will automatically start up a database transaction invisible.
commit () method all the updates cursor, rollback () method of the current cursor rolls back all operations. Every method to start a new business.
Error Handling
API defines a number of errors and abnormal operation of the database DB, the following table lists the errors and exceptions:
